Oh, for a simpler world!
So we’re talking today about contacts, and dry eye. When you’re basically draping a piece of more or less absorbent, flexible material across the top of this incredibly sensitive, moisture-hungry surface of your eye all day, with your eyelids rubbing over it, oh, 20,000 times or so, you would think the question of what it does to the moisture of your eyes could be fairly straightforward to understand - at least more so than what drugs do, or even surgeries.
But that’s really not the case. We’ve had contact lenses around for generations now, a lot longer than many drugs and many surgeries. But our understanding of the relationship between dry eye and contacts is lagging behind, though there have been some important strides made in recent years.
I’m going to briefly walk through a few of the issues that complicate the question of dryness and contact lenses, and then we’ll talk more about the practical side of what to do, both preventively, if you’re concerned about what long term contact lens use might do to your eyes, and reactively, if you’re worried that you’re coming to the end of the line with contacts and you aren’t sure where to go from here.
“Dryness”, or “discomfort”?
One of the really big problems with talking about dry eye and contact lenses is that, in scientific circles, it seems to be surprisingly difficult to distinguish “dryness” from “contact lens discomfort”.
A lot of studies about contacts and dryness discuss dryness entirely from a sensation standpoint. Sensations of dryness, as we know, are all over the map, so that’s a little tricky in itself, but the bigger issue is that the most current definitions of what dry eye is, are quite different from the things most of these studies actually looked at. So let’s talk about those definitions. And to do that, first we need to have a little conversation about:
“Signs”, vs “symptoms”?
If you have dry eye , and you aren’t already familiar with the distinction between “signs” and “symptoms” of dry eye, I want to strongly encourage you to master this one. It’s a crucially important concept to grasp in order to communicate effectively with eye doctors and understand some of the challenges of measuring and treating dry eye.
So signs, or clinical signs, are the clinical measurements of dry eye. They’re things like a Schirmer score, or tear film break-up time, or an osmolarity score, or staining, or meibography.
Symptoms, on the other hand, are all the sensations and experiences you have. As most people with dry eye know, this is rarely confined to a sensation of dryness. It may be watery eyes, it may be burning, it may be grittiness or foreign body sensation, it might be sensitivity to light, or it may be blurred vision, or tired eyes, or eyelids feeling heavy. In a contact lens context, it may be that the contacts irritate your eyes.
The classic problem in dry eye is that signs and symptoms often do not dovetail nicely. That’s a very important issue and we’ll talk about it more another day.
The reason I’m bringing this up here, is that the most current definitions of dry eye include both signs and symptoms, while a lot of the studies about contacts and dry eye look only at symptoms. So researchers can’t know from that whether the problem is what the contacts are doing to your eyes while they’re in, what symptoms they’re giving you, versus what’s going on in your tear system and whether you’re actually acquiring dry eye disease over time by wearing contacts.
So that leads us to make the acquaintance of:
CLIDE, and CLADE?
So CLIDE and CLADE are a couple of things dreamed up by TFOS expert workshops to help us understand the difference.
CLIDE is contact lens induced dry eye. They define it as signs AND symptoms of dry eye happening with contact lens use when there is evidence that you did not have those signs and symptoms before you started wearing the lenses. So this is really the concept we’re going for when we talk about whether contacts cause dry eye, right? Unfortunately the CLIDE concept is so new that very few studies actually conform to its requirements. There is, however, one recent one showing a whopping 42% of daily disposable hydrogel contact lens users experiencing CLIDE, which is pretty impressive.
Then, there’s CLADE.
CLADE is contact lens associated dry eye. That’s where you get signs and symptoms while you’re wearing the lenses, period. You might or might not have had issues before contacts, but the point is that none of it is documented.
Frankly, I’m not sure how useful these distinctions are to you and me - especially since there’s yet another situation that neither CLIDE nor CLADE can answer for, which is all about symptoms without documentation of clinical signs! But the bottom line is that there are some reasonably sound reasons why the scientific community are pretty hesitant to say “Contact lenses cause dry eye”, even when there are so many studies powerfully showing at least some kind of relationship between the two.
And since the question of studies has come up, let’s look at some:
Prominent studies about dry eye and contacts
- In the Canadian Dry Eye Epidemiology Study, 50.1% of contact lens wearers experienced dry eye, compared to 21.7% of non contact lens wearers.
- In a study of 3,443 high school students, contact lens wear was associated with an increased risk of dry eye symptoms in boys and girls.
- In a study in China, 8.4% of high school students had dry eye symptoms while 32.8% of contact lens wearers had dry eye symptoms.
There's lots more, of course, but that's a flavor at least.
How do contacts cause dry eye (if they do)?
So what do we know about what contacts do to the tear system?
According to TFOS DEWS II,
- They can cause “a thinner, patchy lipid layer with poor wettability and impaired spreading capability”
- Tear film instability (reduced NIBUT)
- Increased tear evaporation rate
- Decreased tear film meniscus volume
- Elevated cholesterol levels
- A whole slew of increased or decreased unpronounceable stuff.
- Changes to Langerhans cells, conjunctival goblet cell density and "lid wiper epitheliopathy"
- They can adversely affect meibomian gland expressibility, gland dropout and number of plugged and expressible orifices in the first 2 years of wear
What do the experts say we should do about it?
Here is how TFOS DEWS II looks at dry eye and contact lenses (4.3.3 of the TFOS DEWS II Iatrogenic Dry Eye Report). We can:
- Exclude systemic and ocular disease
- Fit daily disposables
- Fit lenses with internal wetting agents
- Use topical wetting agents
- Use Lacriserts
- Use Omega 3 and Omega 3 fatty acids
- Use plugs
- Use Azasite
- Reduce wearing time
- Or just quit.
My personal thoughts on what this all means?
I’m tempted to share a few things I’ve observed over the years.
First, for everyone who is pushing the limits of their contact lens tolerance:
There is nothing wrong with wanting to continue contact lens wear. There are lot of reasons why people are stubborn about continuing to wear contacts even after they’re having problems or getting really uncomfortable. There are a couple of things I want you to know, and a couple of things I want to encourage you not to do, and a couple things I want to encourage you to do.
What you need to know:
- If your lenses are getting really uncomfortable, you may need a cornea specialist. No disrespect to your optometrist, but there may be things going on that just aren’t getting fully diagnosed because your eye doctor just doesn’t have quite enough expertise.
- Are you one of those people who actually feels like your eyes are more comfortable with your lenses in, than not in?
- Sometimes contacts are irritating because your eyes are dry.
- Sometimes your contacts act as a shield for your dry eyes - but they are just masking what is really going on with your eyes. If you keep wearing them, you’re putting off the inevitable.
Things not to do?
- Don’t get LASIK because of contact lens intolerance. Talk about going from the frying pan into the fire.
- Don’t put off the visit to the specialist.
- Don’t mask it all with over-the-counter drops.
Things to do?
- Get to a specialist - you want a cornea specialist ophthalmologist. Ideally, you want one that actually gives a darn about dry eye specifically, because truth be told, an awful lot of cornea specialist are just LASIK surgeons, and that’s really not what you want!
- If you are motivated to continue contact lens use, look into scleral lenses. They are much more expensive; they are more complicated; they may well be much harder to get and to get used to and to support. But they are actually really good for dry eyes. Scleral lenses are a giant size hard lens that holds fluid against the entire sensitive part of the eye all day. They aren’t for everyone. But for motivated contact lens users, they are amazing both for vision quality and for corneal health